Theodore's manipulation relies a bit too much on things like: you probably wouldn't want to marry a killer, you probably fear for your life, Rishe probably doesn't know Arnold well enough, etc. So saying them would probably have an impact on her relationship with Arnold. Well, it breaks against someone with more knowledge than they're supposed to have, like she has.
"The resolve to be my wife? There's no need for that." +> "I want to make sure that you're happy." Funny how she's still prone to a tilt due to those words and an unexpected kiss.
The nail polish idea was rather well thought, from both Rishe and the author. The business benefits her, Tully, and the general population, specially the ones in the slums. And the maids are more than happy to be the product demonstration; later on they'll basically become walking ad boards for Rishe's nail polish.
I'm not sure on what to think about Rishe using Tully's sister sickness for the business though. Not from a moral standpoint (she's curing someone sick), but from a pragmatic one (would he be really convinced by that?).
Plot twist at the end!